Tactile corpuscle

Tactile corpuscles or Meissner's corpuscles are a type of mechanoreceptor discovered by anatomist Georg Meissner (1829–1905) and Rudolf Wagner.[1][2] They are a type of nerve ending in the skin that is responsible for sensitivity to light touch. In particular, they have their highest sensitivity (lowest threshold) when sensing vibrations between 10 and 50 hertz. They are rapidly adaptive receptors. They are most concentrated in thick hairless skin, especially at the finger pads.

Tactile corpuscle
Papilla of the hand, magnified 350 times.
  1. Side view of a papilla of the hand.
    1. Cortical layer.
    2. Tactile corpuscle.
    3. Small nerve of the papilla, with neurolemma.
    4. Its two nerve fibers (axons) running with spiral coils around the tactile corpuscle.
    5. Apparent termination of one of these fibers.
  2. A tactile papilla seen from above so as to show its transverse section.
    1. Cortical layer.
    2. Nerve fiber.
    3. Outer layer of the tactile body, with nuclei.
    4. Clear interior substance.
Details
LocationSkin
Identifiers
Latincorpusculum tactus
MeSHD008465
THH3.11.06.0.00007
Anatomical terms of microanatomy

Structure

Tactile corpuscles are encapsulated unmyelinated nerve endings, which consist of flattened supportive cells arranged as horizontal lamellae surrounded by a connective tissue capsule. The corpuscle is 30–140 μm in length and 40–60 μm in diameter. A single nerve fiber meanders between the lamellae and throughout the corpuscle.

Location

They are distributed on various areas of the skin, but concentrated in areas especially sensitive to light touch, such as the fingers and lips.[3][4][5][6][7] More specifically, they are primarily located in glabrous skin just beneath the epidermis within the dermal papillae.[8]

Comparison with other receptors

Feelings of deep pressure (from a poke, for instance) are generated from lamellar corpuscles (the only other type of phasic tactile mechanoreceptor), which are located deeper in the dermis, and some free nerve endings.

Also, tactile corpuscles do not detect noxious stimuli; this is signaled exclusively by free nerve endings.

Development

The number of tactile corpuscles per square millimeter of human skin on the fingertips drops fourfold between the ages of 12 and 50. The rate at which they are lost correlates well with the age-related loss in touch sensitivity for small probes.[9]

Function

Tactile corpuscles are rapidly adapting mechanoreceptors. They are sensitive to shape and textural changes in exploratory and discriminatory touch. Their acute sensitivity provides the neural basis for reading Braille text. Because of their superficial location in the dermis, these corpuscles are particularly sensitive to touch and vibrations, but for the same reasons, they are limited in their detection because they can only signal that something is touching the skin.[10]

Any physical deformation of the corpuscle will cause sodium ions to enter it, creating an action potential in the corpuscle's nerve fiber. Since they are rapidly adapting or phasic, the action potentials generated quickly decrease and eventually cease (this is the reason one stops "feeling" one's clothes).[10]

If the stimulus is removed, the corpuscle regains its shape and while doing so (i.e.: while physically reforming) causes another volley of action potentials to be generated.

Additional images
  • "Meissner's corpuscle" labeled at upper right
  • Diagrammatic sectional view of the skin.
  • light micrograph

References
  1. "Georg Meissner". www.WhoNamedIt.com. Retrieved 30 January 2017.
  2. Paré, Michel; Joseph E. Mazurkiewicz; Allan M. Smith; Frank L. Rice (15 September 2001). "The Meissner Corpuscle Revised: A Multiafferented Mechanoreceptor with Nociceptor Immunochemical Properties". The Journal of Neuroscience. 21 (18): 7236–46. doi:10.1523/JNEUROSCI.21-18-07236.2001. PMID 11549734.
  3. Cauna, Nikolajs; Ross, Leonard L. (1 October 1960). "The fine structure of Meissner's touch corpuscles of human fingers". The Journal of Cell Biology. 8 (2): 467–82. doi:10.1083/jcb.8.2.467. PMC 2224947. PMID 13691669.
  4. Hoffmann, Joscelyn N.; Montag, Anthony G.; Dominy, Nathaniel J. (November 2004). "Meissner corpuscles and somatosensory acuity: the prehensile appendages of primates and elephants". The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology. 281 (1): 1138–47. doi:10.1002/ar.a.20119. PMID 15470674.
  5. Martini / Bartholomew (2010) [1995]. Essentials of Anatomy and Physiology 3E. Pearson Benjamin Cummings.
  6. Afifi, Adel K.; Ronald Arly Bergman (2005) [1998]. Functional neuroanatomy: text and atlas. McGraw-Hill Professional. p. 16. doi:10.1036/0071408126. ISBN 978-0-07-001589-0. 10.1036/0071408126.
  7. "Nervous system - Touch". BBC. Retrieved 7 May 2010.
  8. Winkelmann, R. K. (1959-01-21). "The Erogenous Zones: Their Nerve Supply and Significance". Proceedings of the Staff Meetings of the Mayo Clinic. 34 (2): 39–47. PMID 13645790.
  9. Thornbury, Julia M.; Mistretta, Charlotte M. (January 1981). "Tactile sensitivity as a function of age". Journal of Gerontology. 36 (1): 34–9. doi:10.1093/geronj/36.1.34. PMID 7451834.
  10. Bear, Mark F.; Connors, Barry W.; Paradiso, Michael A. (2016). Neuroscience : Exploring the Brain (4th ed.). Philadelphia: Wolters Kluwer. pp. 416–422. ISBN 9780781778176. OCLC 897825779.

Sources
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.